Seized 93cr250, Tony91 or anyone else

[gator kdx]

After about 1hr of riding this past Saturday my 93cr250 seized up going when doing a fairly long run - I was at about 2/3 throttle and jetted on the rich side so still not sure how or why it seized.

Anyhow, all of a sudden the motor started making a 'whining' sound and felt like it was slowing down then a telltale clunk (all of this happened in less than a second). I pulled in the clutch and came to a stop as fast as possible.

A friend and I pulled the cylinder and piston and both look worn but no obvious damage like I would expect from the seize. When the cylinder came off their was a piece of metal - about the 1/4inch circular - sitting on top of the crank.

I have done top ends before but never the bottom. I am worried that splitting the cases is going to be required. The biggest problem I have noticed so far is that when I turn the crank, at the bottom their is about 1/4 inch of vertical play. At the top (TDC) the crank seems to bind up and not want to pivot.

My previous bike was a 90kdx200 which I ended up pouring money into and I really can't afford to do that again. If anybody has any ideas or suggestions I could use the advice.

Thanks

 

[blanc]

Sounds like the conrod is bent.

 

[capt hookleg]

Any vertical play in the rod from the crankshaft is not good. You will need to rebuild/replace the crankshaft and rod. Plan on replacing the main bearings and seals at the same time. One thing to look into is the aftermarket complete crankshafts from Wiseco, ready to install. Some deals can be found on different parts warehouses ie rocky mountain M/C. Splitting the cases isn't too bad. Buy a good service manual, and you will need a puller to remove the crankcase from the crank. I have use a dampener puller for an automobile, You will have to find some long metric bolts, or make your own from 1/4" bolts. When installing the crank, place it in the freezer for a few hours in a plastic bag and heat the main bearing with a heat gun or wifey's hair dryer. It will drop into place without having to hammer on the crank, this will help to keep it more true. The same thing will work when installing the main bearing into the crank halves. Freeze the bearings and heat the crank half. Good luck.

 

[dirt bike dave]

The big end bearing on my '99 went out last year; sounds like yours went, too. 

OEM Honda crank assemblies are not too expensive if you go through Service Honda or someone that will match their prices; probably around $170 or so (I think that's how much my '99 was).  The Honda OEM crank/rod assembly is reportedly better quality than the Wiseco.

Besides the crank/rod assembly and crankshaft bearings ($30+- x 2), you will need a complete gasket set ($70+-) and a top end kit ($100 or so for piston, etc...)  Add in a few other miscl. items and you are probably looking at around $450 in parts, not including special tools or labor.

If the crankcase halves are damaged, they may need to be repaired or replaced as well (Honda sells the halves individually, about $170 inlcuding crank bearing).  You probably won't be able to tell if there is damage there until after you split the cases.

 

[gator kdx]

I was hoping eric gorr could do it - so I knew it was done right - but he said he is backed up for 2-3 weeks right now. I'm keeping my fingers crossed it is just the connecting rod and crank and that there was no damage to the case sides.

My riding has been getting a lot better lately though and I hate to take what would probably end up being a month off. I'm in Florida so it might be cold but not so nasty that you can't ride.

I guess the big question is, I've done top ends several times but never done a bottom end. Is it worth the extra money to have someone else do it (at least the tough parts like pressing bearings and splitting the cases) or should I attempt it myself.

I'm pretty mechanically inclined but I don't have any of the specialty tools it sounds like I might need (case splitter, flywheel puller, clutch holder, etc). I've got the service manual, searched the forum for bottom end posts, and read the articles on eg's site about bottom end and crank repair.

Please let me know if you recommend I do it myself or send it off. Also, let me know what tools I need and don't need. I've heard lots of horror stories about people doing costly damage and want to find out how risky this job is.

Thanks

 

[dirt bike dave]

For mine, I did most the disassembly myself, up to pulling the clutch basket and flywheel.  I paid a pro at a private shop a little over $200 to complete the disassembly, check over all the parts (inc. cylinder) for damage and completely reassemble the motor (top and bottom ends).  I put the motor back in the bike myself.

The complete motor weighs about 55 pounds not including your new parts, so if you are sending it out, you are looking at some $ in shipping & insurance plus the added time. 

I would call a local shop and see if you can get a quote.  If they just pull the flywheel, clutch basket and split the cases (the stuff you can't do with your own tools) it should be less than an hour of shop time. If you want a complete reassembly like I did, you are probably looking at 4-6 hours of shop time.

As to whether you should do it yourself, I can't answer that for you.  But keep in mind you are going to spend a lot more time than a pro would take, plus you will have to round up the specialty tools.  And you might not do as good a job as someone who has done it 100 times before.  For the peace of mind and less hassle, going with a pro might make the most sense.

On an older bike, it's tough to justify spending lots of money to get it running again, as that money could go towards a newer bike. 

Good luck with whatever you decide to do.

 

[gator kdx]

Its definitely a tough call....I just moved and I've only been in Tallahassee for a couple of months. From what I hear the local places don't have a great reputation. I called a couple of them earlier today and they all said they could get it back to me in 3 weeks - for 3 weeks I would just send it to Gorr.

Plus they were talking about charging me 2+ hours of labor just for splitting the cases if I bring in the bottom end.

How easy is it to screw things up? I'm tempted to buy the harmonic balancer I saw at Sears for $20 and give it a shot.

I appreciate the feedback, please keep it coming.

 

[Mr. Clean]

It is obvious to me that you really want to do the job yourself. I think you should do it! I split my first case at age 19 with minimal tools. Just use common sense and respect the gasket surfaces and you should do fine. Give yourself plenty of time so you will enjoy it. Good luck and save some money!

Mr. Clean

 

[gator kdx]

Sounds like you figured me out Mr. Clean. I do want to give it a shot. What tools are absolutely required and what tools can I live without - or use something else that's similar.

From looking at the service manual it seems like I need 5 or 6 'specialty tools' which I'm sure cost a fortune. Just to mention a few, they say I need a:
-gear holder (for primary drive & driven gear)
-universal holder (holding the sprocket while I remove the bolt)
-crankcase splitting tool
-universal bearing puller
-bearing driver
-crankcase assembly tool??

If it helps, I plan on getting one of the pre-assembled Wiseco cranks with the hot-rod conrod.

Thanks for the replies, more tips or if anyone knows of a website with a good photo-walkthrough of the process are very greatly appreciated.

 

[txkawboy]

i urge u to try it; it reminds me if a lengthy jigsaw puzzle: not hard, just time-consuming and exact...your second one will be 50% easier.
a few things i would tell u to do:
1. buy a $20 air impact wrench ---see harborfreight.com, etc, near you...
this will aloow u to skip most of the special tools, and the others my post will tell u how to make for pennies. u know how tightly to reinstall the nuts by using the lowest power-setting possible when u remove them, usually #1 or #2, and USE LOCTITE!
2. cheap air compressor
3. a $20 1/4" drive air ratchet --do NOT use 3/8 on a bike for 90% of your bolts! u can buy a $4 "air pressure regulator" that would enable u to use a 3/8, but i dont risk it...
4. eric gorr's book, or at least read his excerpts; ericgorr.com...the book taught me tons, and i have been doing this for over 20 years.
5. read my 11-23-03 "No more broken levers..." posting under the Maintenance forum; tons of tricks/tips to save u tons of $$$, like the fact that bearings and seals can be bought for PEANUTS from your local industrial-bearing house...!! I just rebuilt a buddy's '94 RM250/320 bottom end, crank seals/bearings, for less than $40 this way...read it and weep! <G> You need to get the ID and OD of your parts, or better yet bring them with you, is all...

Good luck man, and ps--u have 3 of the finest motorcycles ever made, period. they all do what they were meant to do with perfection, sans that underwaer-soiling CR headshake! 8>]

 

[gator kdx]

I actually just picked up another bike as well, 2001 yz250 - also in need of bottom end work.

So looks like I'll be getting plenty of practice. I'm really looking forward to getting both the newer yz and older cr running well again. I'm curious how much difference I will be able to tell.

The brief ride I gave the yz -before I decided to bench it until bottom end work is finished- it didn't seem like it had more power or torque than the cr.

Yeah, they are both 250s but I figured that almost 10 years newer and more hp would have been more noticeable.

I'm curious what kind of differences I can expect.

 

[dirt bike dave]

Gator - The basic CR250 engine design went unchanged for a long, long time. Your '93 CR250 engine had only minor changes&nbsp;all the way through '01.&nbsp; The differences between those years are refinements to cylinder porting, ignition, carbs and exhaust pipes.&nbsp;

The changes were not really to get more HP, but to alter power delivery to what Honda wanted&nbsp;to sell&nbsp;that year.&nbsp; For example, my '99&nbsp;is a 'mellow'&nbsp;year compared to the&nbsp;more hyper '97, but lots of people like the '99 better even though it&nbsp;has less peak power.&nbsp;&nbsp;

If you can find a newer CR up to '01 with a trashed cylinder, you should be able to&nbsp;drop the bottom end&nbsp;into your old bike, or put your&nbsp;good cylinder on the newer machine.

FWIW, many of the newest engine designs save weight and might have slightly more power potential.&nbsp; But if properly tuned, your '93 should make plenty of power and not give away much to&nbsp;most newer 250s.&nbsp; The big changes to the new bikes are suspension - that's improved a lot over 10 years!

&nbsp;

 

[gator kdx]

Yeah, one of the biggest factors in me picking up the yz was the modern suspension. The previous owner had the suspension completely re-worked for a rider of his weight and ability (which luckily are very similar to mine).

Mostly been trail riding lately and I've got a moderate variety of terrain here in north florida (lots of whoops, hardpack, tons of sugar sand, minor hills, fun little jumps). I'm hoping that the biggest difference in the two bikes will be the suspension - which will hopefully translate to speed.